load rating custom made lifting piece

[bushmill]

I'm trying to analyze a custom made "lifting cap" to find the safe working load.

This consists of a 16" diameter steel caisson 12" long with 0.565" thick walls welded to a 1" thick plate (at bottom). The caisson is threaded at the top and will be attached to a rig. The eyelet is 2 inches thick and welded to 1" plate at bottom. Since it should all be loaded in tension (downward) I'm expecting the weak part to be the 1" plate. But I don't know how to check a circular plate for bending with a distributed line load... can anyone help?

 

[JStephen]

If you split the plate down the middle, and sum moments about that line, you'll just have half the load acting at the centroid of a semi-circle (I think that's 2R/pi, but double check). That will give you the average moment along that line, and you can figure the peak moment would be somewhat higher. That's probably the best you'll do without finite element analysis.

Roark may have a load case resembling that, but I don't remember seeing one before.

 

[robyengIT]

Roark's formulas for stress and strain - 7th edition :
Table 9.1 case 1 or
Table 9.2 case 4 and case 15(changing sign)
Furthermore for the eyelet : I should make a slot on the plate 1" thick so to insert the eyelet plate and weld on both sides of the plate 1" thick

 

[Lomarandil]

If it's a lifting device in the US, you'll need to load test it anyway (ASME BTH/OSHA) -- so run the calcs to get a rough idea for your test load and configuration, but I wouldn't worry about sharpening the pencil too much unless you really need to.

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The name is a long story -- just call me Lo.